Hydroxypropyl methylcellulose (HPMC for short) has excellent thickening properties and can be used as an excellent concrete anti-dispersion agent.

In recent years, with the continuous development of exterior wall insulation technology, the continuous progress of cellulose production technology, and the excellent properties of HPMC itself, HPMC has been widely used in the construction industry.

The setting time of concrete is mainly related to the setting time of cement. The effect of aggregate is not significant. Therefore, the setting time of mortar can be used to replace the study of the effect of HPMC on the setting time of underwater non-dispersible concrete mixtures.

Since the setting time of mortar is affected by the water-cement ratio and the mortar-sand ratio. In order to evaluate the effect of HPMC on the setting time of mortar, the water-cement ratio and mortar-sand ratio of the mortar need to be fixed.

Experimental reactions show that the addition of HPMC has a significant retarding effect on the mortar mixture.

And with the increase of HPMC dosage, the setting time of the mortar is successively extended. Under the same HPMC dosage, the setting time of underwater mortar is longer than that of mortar formed in the air.

When measured in water, the setting time of the mortar mixed with HPMC is compared with the blank specimen. The initial setting is delayed by 6~18 hours, and the final setting is delayed by 6~22 hours. Therefore, HPMC should be used in combination with an early strength agent.

HPMC is a high molecular polymer with a macromolecular linear structure. The functional group has hydroxyl groups, which can form hydrogen bonds with the mixing water molecules. The viscosity of the mixing water is increased.

The long molecular chains of HPMC will attract each other. The HPMC molecules are entangled with each other to form a network structure. The cement and mixing water are wrapped.

Because HPMC forms a network structure similar to a film and wraps the cement. It will effectively prevent the volatilization of water in the mortar. It hinders or slows down the hydration rate of cement.